Power holdup circuit

Abstract

A power holdup circuit including a monitoring circuit and a power holdup circuit. The monitoring circuit includes an average voltage comparator and an absolute voltage comparator which cooperate to detect a voltage drop in the voltage supplied by the power supply. The monitoring circuit also includes a timer to determine the time period of the voltage dropout. If a predetermined voltage dropout event occurs, the monitoring circuit generates a control signal to a switching component which activates a holdup power source. The holdup power source includes an energy storage device that stores energy to maintain the supply voltage during dropout periods.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0002]This application is a continuation-in-part of U.S. patent application Ser. No. 10 / 255,425 filed on Sep. 26, 2002. The disclosure of the above application is incorporated herein by reference.FIELD OF THE INVENTION[0003]The present invention relates generally to systems for controlling line voltage, and more particularly to a circuit for maintaining power during line voltage dropouts in, for example, power conversion equipment.BACKGROUND OF THE INVENTION[0004]Power factor relates generally to the efficiency of a system in using power and is preferably maintained at a high level (i.e., 0.9 or higher) to minimize losses. In particular, power factor defines the relationship between the actual / active or real power being used by the system (i.e., measured in kilo-Watts (KW)) and the total power supplied and available to the system. Further, total power is defined by apparent power (i.e., measured in volt-amps (VA)), which includes a non-working ...

AI Technical Summary

Benefits of technology

[0012]The present invention generally includes a circuit and method of providing the same that has holdup capability with a high power factor during line voltage dropout. The circuit is less complex in design and requires no external monitoring and control for providing the holdup capability. The present invention monitors the input voltage to a system and switches to a holdup power source when needed (e.g., during a single cycle line voltage dropout). Power from the primary source (i.e., line voltage) is restored after the dropout condition ends. The holdup power source is appropriately charged based upon the input power source to the system and the requirements of the system.

Problems solved by technology

Reactive power is generally not useful power, and typically provides for sustaining the electromagnetic field in systems.

However, when the current from a power source includes harmonics, or when it is not in phase with the voltage (e.g., reactive device), the power factor of the system is reduced (i.e., less than 1), thus indicating a less efficient system.

Depending upon the power supplier, the cost of receiving power may increase if power factor is not sustained at a specific minimum level (i.e., 0.9).

Additionally, larger wiring and transformers may be needed when power factor is low.

Thus, a low power factor may have numerous negative effects on different aspects of a system.

When a power factor above 0.9-0.95 is desired or required, the size and weight of the inductor becomes prohibitive.

However, although these PFC devices provide higher power factors (i.e., above 0.9), these devices are complex, resulting in their size and cost increasing significantly.

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